Gas gravitometers



3 Sheets-Sheet 1 Filed Aug. 18, 1961 INV EN 1 OR V /V w 2 J v F n. m f A ATTORNEYS May 4, 1965 J. w. BARTLETT GAS GRAVITOMETERS 3 Sheets-Sheet 2 Filed Aug. 18, 1961 INVENTOR Joseph W. Barf/eh WM BY ATTORNEYS United States Patent Ofiice 3,181,345 Patented May 4, 1965 3,181,345 GAS GRAVHTGMETERS Joseph W. Bartlett, 11767 Valley Dale Drive, Dallas, Tex. Filed Aug. 18, 1961, Ser. No. 132,385 9 Claims. (Cl. 73-30) This invention relates to new and useful improvements in gas gravitometers.

More particularly, the invention relates to means for accurately determining, under ambient conditions, the specific gravity of gases relative to the density of air at a pressure of one atmosphere and at a selected base temperature, while compensating for altitude, variations in barometric pressure and ambient temperature and, preferably, for humidity in the atmosphere.

Basically, the invention involves the measurement of the differences in weights of a column of gas and a column of equal height of air which is preferably dry. The height of both columns is varied in direct proportion to the absolute ambient temperature and inversely in proportion to the barometric pressure. For example, a six foot column of dry air at 30 inches of mercury and 60 F. (520 absolute) exerts a pressure at its base of 0.460 pound per sqaure foot plus the barometric pressure at its top, while a six foot column of gas having a specific gravity of 0.60 under the same conditions exerts a base pressure of 0.276 pound per square foot. The difference of 0.184 pound per square foot may be measured and recorded as Sp. G.=0.60. In the event that the absolute ambient temperature increases by to 572 (112 F), the barometric pressure remaining at 30 inches of mercury, the density of both the air and gas is reduced by 10% and the difference in pressures is reduced by 10%. If, however, the height of both columns is increased by 10%, the pressure difference is restored to 0.184 pound per square foot and the effect of the temperature change is compensated. Likewise, if the barometric pressure falls by 2%, the difference between the pressures at the bases of the air and gas columns decreases by 2% unless compensated by increasing the height of both columns by 2%. A decrease in temperature or increase in barometric pressure produces effects opposite to the foregoing effects and can be compensated by decreasing the height of both columns in proportion to the change.

As is known, the specific gravity of gases lighter than air is inversely proportional to the pressure differential and directly proportional for gases heavier than air. Thus, the difference in pressures at the bases of six foot columns one of which contains dry air and one containing a gas having a specific gravity of 0.50, when measured at 30 inches of mercury and 60 F., is 0.230 pound per square foot.

One object of the invention is to provide improved means for accurately determining the specific gravity of gases with substantially no error due to humidity in the atmosphere and ambient temperature and barometric pressure variations.

An important object of the invention is to provide improved specific gravity determining means having a pair of columns of air and gas of equal but variable height and means for varying the height of the air and gas columns in direct proportion to the absolute ambient temperature and in inverse proportion to the barometric pressure.

A particular object of the invention is to provide improved means for accurately determining the specific gravity of gases by measuring the difference in the pressures at the bases of a pair of columns of equal height having their upper ends open to the atmosphere and containing air and the gas to be tested.

Another object of the invention is to provide an improved gas gravitometer, of the character described, having novel means for varying the height of the columns of air and gas in direct proportion to the absolute ambient temperature and in inverse proportion to the barometric pressure.

A further object of the invention is to provide an improved gas gravitometer, of the character described, wherein the air and gas columns are expansible and contractasle and have connection with an expansible and contractable, closed column of dry air or other gases under pressure and of sufiicient volume to expand it to the correct height at the time of setting whereby the closed column is responsive to variations in the barometric pressure and ambient temperature and expands and contracts to raise and lower the height of said air and gas columns in proportion to the quotient of absolute ambient temperature divided by the barometric pressure.

Still another object of the invention is to provide an improved gas gravitometer, of the character described, wherein the columns may be in the form of tubes having telescoping, liquid-sealed connections at their lower ends to the upper ends of stationary tubes and connected to one another so as to be movable in unison with the movement of the telescoping tube of the closed column of dry, compressed air.

Another object of the invention is to provide an improved gas gravitometer, of the character described, which is of rugged, inexpensive construction and which is adapted to accurately measure the specific gravity of gases that are lighter or heavier than air.

A construction designed to carry out the invention will be hereinafter described, together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, wherein examples of the invention are shown, and wherein:

FIG. 1 is a transverse, vertical, sectional view of a gas gravitometer constructed in accordance with the inven tion for gas lighter than air,

FIG. 2 is a transverse, vertical, sectional view of a portion of a modified tube construction for the closed column of dry, compressed air,

FIG, 3 is a view, similar to FIG. 1, of a modified gravitometer for gas heavier than air, and

FIG. 4 is a view, similar to FIG. 1, of another modification for gas heavier than air.

In the drawings, the numeral 10 designates a gas gravitometer which includes a trio of upright columns 11, 12 and 13 of equal height, a pressure responsive member 14 having its housing 15 communicating with the lower ends of the columns 11 and 12, a pair of bases or pedestals 16 and 17 for supporting the columns 12 and 13 and a clock-actuated, rotatable chart 18. The column 11 has a lower, cylindrical tube or tubular section 19 supported by the top of the housing 15 of the member 14 and communicating with the interior thereof, while the columns 12 and 13 have similar tubes or sections 20 and 21, respectively, upstanding from the bases 16 and 17. A fluid conductor 22 extends from the bottom of the tube 20 through the base 16 and communicates with the lower portion of the housing 15. Complementary, upper tubes or sections 23, 24 and 25, of slightly greater diameter, have their lower end portions telescoping the upper end portions of the tubes 19, 20 and 21 and coacting therewith to provide columns of variable height. The upper portions of the telescoping tubes 23, 24 and 25 are rigidly connected to one another by suitable brackets 26 so that said tubes are movable in unison. Preferably, liquid seals are provided for the telescoping connections of the tubes and may be in the form of concentric wells or sleeves 27, 28 and 29 having closed bottoms or lower ends secured to the upper portions of the lower tubes so as to surround the lower portions of the upper tubes in spaced relation and containing a suitable liquid 30. It is noted that the telescoping connections may be sealed in any suitable manner and that flexible tubing or bellowstype expansible tubing could be utilized for the columns 11 and 12.

The column 11 is adapted to receive the gas to be tested and may have a burner 31 and overlying flue or stack 32 at the upper end of its telescoping tube 23 if said gas is combustible. As shown by the numeral 33, the burner 31 is spaced above the upper end of the tube to admit air to said burner without affecting the height of the column. A pipe or conductor 34 communicates with and upstands axially from the top of the housing of the pressure-responsive member 14 for supplying gas to the interior thereof from an enlarged compartment or casing 35 at the upper end of the pipe. The compartment 35, which has a gas inlet 36, is offset laterally of the pipe 34 to permit the pivotal mounting therein of a beam 37 with one end in substantial alinement with the bore of the pipe. A reciprocal rod 38 is suspended from the latter end of the beam 37 so as to depend axially through the pipe into the housing 15, while a counterbalance weight 39 is attached to the opposite end of said beam. The gas inlet 36 is located adjacent the upper end of the compartment to permit purging of the gas therefrom as well as the upper portion of the housing and the column 11. A stylus or pen arm 40 extends upwardly from and has rigid connection with the beam at its pivot axis for recording the movement thereof upon the rotatable chart 18.

Reciprocation may be imparted to the rod 38 by a bell 41, of inverted cup shape, welded or otherwise secured to its lower end portion and disposed within the housing between its communication with the tube 19 and conductor 22. The housing 15 has an annular sump 42, externally of its connection to the conductor, for receiving the complementary skirt 43 of the bell 41 and an axial well 44 for a solid metal float 45 fixed on the lower extremity of the rod which extends below said bell. For counterbalancing the weight of the bell and float, the sump 42 and well 44 are substantially filled with mercury or other liquid having a low vapor pressure and, preferably, high density. Also, the liquid in the sump seals off the interior or lower surfaces of the bell from its exterior or upper surfaces whereby the upper surface of said bell is exposed to the pressure at the base of the column 11 resulting from the weight of the gas flowing through said column. The bell 41 and float 45 are so proportioned that said bell floats in its lowermost position at Sp. G.=1.0 and in its uppermost position at Sp. G.=0. A valved drain 46 communicates with the interior of the housing below and within the bell and above the mercury in the sump and well to permit purging of the column 12 through the conductor 22.

The column 12 is adapted to contain air at ambient temperature and barometric pressure for supplying the same to the underside of the bell 41. As shown by the numeral 48, the upper end portion of the telescoping tube 24 may be enlarged to provide a container for silica gel or other desiccant 49. A removable cap or lid closes the upper end of the container 48 and one or more air inlet openings 51 are formed in the side of said container above the desiccant 49. It is noted that the openings 33 and 51 are in substantially horizontal alinement so that the columns 11 and 12 are of the same height, the efiective base of said column 11 being at the upper surface of the bell 41. Since the conductor 22 establishes communication between the lower end of the tube and the underside of the bell 41, the pressure at the base of the column 12, created by the weight of the air therein and the barometric pressure at the top of said column, is exerted against said bell so as to urge the same upwardly.

The column 13 is of much larger diameter than the columns 11 and 12 and its tubes 21 and have lower and upper closed ends or bottom and top walls 52 and 53, respectively. An angular fitting or pipe 54 extends through the bottom wall 52 and base 17 and has a manual valve 55 mounted therein to permit the column to be filled with dry air or other gases under pressure slightly greater than atmospheric and of sufiicient volume to elevate the tube 25 to the correct height at the time of setting. Due to the rigid connection provided by the brackets 26, the tubes 23 and 24 move with and are maintained at the same elevation as the tube 21. To permit purging of the column 13, a plug 56 is removably mounted in the top wall 53 of the tube 25. This column functions as an expansible and contractable chamber responsive to variations in the ambient temperature and barometric pressure and its height varies inversely as the barometric pressure and directly as the absolute ambient temperature. When the column 13 is properly proportioned, the dry air therein expands and contracts to raise and lower the tube 25 as well as the tubes 23 and 24 in proportion to the quotient of absolute ambient temperature divided by the barometric pressure. If desired, the lower portion of the tube 21 and the upper portion of the tube 25 may be provided with internal and external radial fins 57 and 58 to facilitate heat transfer (FIG. 2). It is noted, however, that the column 13 as well as the entire gravitometer should be shielded from external radiant heat.

In operation, the gas to be tested is admitted through the inlet 36 so as to fill and flow continuously through the compartment 35, the pipe 34, the upper portion of the housing 15 and the tubes 19 and 23 of the column 11 to and through the open upper end of said tube 19. If combustible, the gas is ignited at the burner 31. The weight of the gas at the base of the column 11 exerts a pressure on the upper surface of the bell 41, while the underside of said bell is exposed to the pressure at the base of the air column 12. The gas being lighter than air, the bell is lifted by the greater air pressure so as to raise the rod 38 and pivot the beam 37 and arm 40 counterclockwise. Due to this upward movement, the buoyancy of the bell is decreased by the partial withdrawal of its skirt 43 from the liquid in the sump 42 so as to counterbalance a portion of the pressure differential above and below said bell. Consequently, the bell 41 is lifted only a small distance. When the absolute ambient temperature increases or decreases and the baroinetric pressure remains unchanged, the density of the gas and air and the pressure differential therebetween are reduced or increased accordingly. Since the dry air or other gas in the closed column 13 is responsive to temperature changes, it expands upon a temperature increase so as to elevate the tube 25 and raise the height of said column and contracts upon a temperature decrease so as to lower said tube and reduce the height of said column. As has been explained, the tubes 23 and 24 move upwardly and downwardly with the tube 25 so as to raise and lower the height of the columns 11 and 12 and thereby compensate the increase or decrease of the pressure differential caused by the change in temperature. Also, the height of the gas and air columns 11 and 12 is decreased and increased upon rise and fall of the barometric pressure by contraction and expansion of the dry air or gas in the closed column which lowers and raises the tube 25. It is noted that the liquid-sealed bell 41 is preferred because it is capable of measuring very small pressure differentials.

When the gas is heavier than air, a modified gravitometer 10' may be provided as shown in FIG. 3 wherein prime numerals identify similar elements. The gas column 11' is mounted on the base or pedestal 16' and the lower end of its tube 19' is connected to the lower portion of the housing 15 of the pressure-responsive member 14 so that the pressure at the base of said gas column is exerted upon the underside of the bell 41'. In order to exert its base pressure against the upper surface of the bell, the air column 12' is mounted on the top of the housing 15 so as to communicate with the upper portion of the interior thereof. A gas inlet 36' communicates with the lower portion of the housing 15 in place of the drain 46 and a valved fitting 46 is connected to the compartment 35' in place of the inlet 36. The housing and its sump 4-2 and well 44' are of greater depth than the housing 15 and its sump 42 and well 44, and the skirt 43' of the bell 41 and the lower extremity of the rod 38 are of greater length than the bell skirt 43 and the lower extremity of the rod 38 so as to permit greater travel of said bell 41'. As shown, the bell 41' is in its lowermost position at Sp. G.:1.0.

A sleeve or well 59, having a closed bottom, is secured to the upper end portion of the telescoping tube 23 of the gas column 11' so as to concentrically surround said tube and extend above its upper open end 60 which is in substantially horizontal alinement with the opening 51' of the desiccant container 48' of the telescoping tube 24 of the air column 12'. The container 48 and well 59 are rigidly connected by brackets 25 to the telescoping tube 25 of the closed column 13'. An angular discharge pipe 61 depends from the well 59 into another well 62 which is secured to the well 27 by brackets 63 and which has a conductor 64 depending therefrom for conducting the heavy gas to a point of disposal (not shown). With the exception that the pressure of the gas at the base of the column 11' urges the bell 41' upwardly and the base pressure of the air column 12' urges said bell downwardly, the gravitometer functions in the same manner as the gravitometer 10 to measure the specific gravity of said gas.

Another modified gravitometer 110 for measuring the specific gravity of gas heavier than air is shown in FIG. 4 and includes a gas column 111, identical to the gas column 11' of FIG. 3 and having similar elements 119, 123, 127 and 159454, inclusive. The gas column 111 is mounted on the top of the housing 115 of the pressureresponsive member 114 in the same manner as the gas column 11 of FIG. 1 whereby the lower end of the tube 119 communicates with the upper portion of the interior of said housing above the bell 141. Although identical to the bell 41', the bell 141 is in its uppermost position at Sp. G.=1.0 and the beam 137 is pivoted counterclockwise so as to dispose the stylus or pin of the arm 140 near the center of the chart 113. As shown by the numeral 145, the float is larger than the float 45 and is in the upper portion of the well 144 which is of larger diameter than the well 14. The sump 1 .2, bell skirt 143, and valved drain 145 are identical to the sump 42, skirt 43' (FIG. 3) and drain 46 (FIG. 1), while the pipe 134, compartment 135, gas inlet 136, beam 137 and rod 133 are identical to pipe 34, compartment 35, inlet 35, beam 37 and rod 38. Since the air and closed columns 112 and 113 are identical to the columns 12 and 13, the numerals 116, 117, 120426, 128-130 and 148-156 designate the similar elements thereof. The conductor 122 establishes communication between the lower end of the tube 120 of the column 112 and the lower portion of the interior of the housing 115 whereby the bell 141 is urged upwardly by the pressure at the base of said column. Except for the reverse movement of the bell 141, the gravitometer 1111 functions in the same manner as the gravitometer 10' of FIG. 3.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

l. A gas gravitometer including a pair of upright columns of equal variable height and having upper ends open to the atmosphere, one of the columns containing air at ambient temperature, the other of said columns having a gas to be tested flowing therethrough, pressureresponsive means communicating with the lower ends of said columns for actuation by the differences in pressures at the bases of said columns, means for recording the actuation of the pressure-responsive means, and compensating means responsive to variations in the ambient temperature and barometric pressure and having connection with said columns for increasing and decreasing the height thereof in direct proportion to the ambient temperature and in inverse proportion to the barometric pressure, the compensating means including an expansible closed chamber containing a gas under pressure and of sufiicient quantity to maintain the height of said columns in accordance with the ambient temperature and barometric pressure.

2. A gas gravitometer as set forth in claim 1 wherein the chamber and gas and air columns each include a lower stationary member, an upper member having telescoping sealed connection with each lower member so as to be movable relative thereto, and means connecting the upper members to one another for movement in unison.

3. A gas gravitometer as set forth in claim 2 wherein the expansible closed chamber includes a lower stationary member, an upper member having telescoping sealed connection with the lower member so as to be movable relative thereto, and means connecting the upper member to the gas and air columns for transmitting the movement of said upper member thereto.

4. A gas gravitometer including a pair of upright columns of equal variable height and having upper ends open to the atmosphere, one of the columns containing air at ambient temperature, the other of said columns having a gas to be tested flowing therethrough, pressureresponsive means communicating with the lower ends of said columns for actuation by the difierences in pressures at the bases of said columns, means for recording the actuation of the pressure-responsive means, and compensating means responsive to variations in the ambient temperature and barometric pressure and having connection with said columns for increasing and decreasing the height thereof in direct proportion to the ambient temperature and in inverse proportion to the barometric pressure, the pressure-responsive means including a housing containing a liquid, a bell partially immersed in the liquid so that its upper and lower surfaces are sealed off from each other, the upper surface of the bell being exposed to the pressure at the base of one of said columns and the lower surface of said bell being exposed to the pressure at the base of the other of said columns, and means connecting said bell to the recording means.

5. A gas gravitometer as set forth in claim 4 wherein the compensating means includes an expansible closed chamber containing a gas under pressure and of sufficient quantity to maintain the height of the gas and air columns in accordance with the ambient temperature and barometric pressure.

6. A gas gravitometer including a pair of upright columns of equal height and having open upper ends, each column having a pair of telescoping members so as to be variable in height, one of the columns having a gas to be tested flowing therethrough, the other of said columns containing air at ambient temperature, pressureresponsive means communicating with the lower ends of the lower members of said columns for actuation by the differences in pressures at the bases of said columns, means for recording the actuation of the pressure-responsive means, and compensating means responsive to variations in the ambient temperature and barometric pressure and having connection with the upper members of said columns for raising and lowering said members to increase and decrease the height of said columns in direct proportion to the ambient temperature and in inverse proportion to the barometric pressure.

7. A gas gravitometer as set forth in claim 6 wherein the compensating means includes an upright expansible 7 closed chamber containing a gas under pressure and of sufficient volume to maintain the height of the gas and air columns in accordance with the ambient temperature and barometric pressure.

8. A gas gravitometer as set forth in claim 6 wherein the chamber has a pair of telescoping members of greater diameter than the members of the gas and air chambers, and means connecting the upper members to one another for movement in unison.

9. A gas gravitometer as set forth in claim 6 wherein the pressure-responsive means includes a housing containing a liquid, a bell partially immersed in the liquid so that its upper and lower surfaces are sealed off from each 5 said bell to the recording means.

References Cited by the Examiner UNITED STATES PATENTS 2/38 Binckley 7330 6/53 Binckley 73-30 RICHARD C. QUEISSER, Primary Examiner. 

6. A GAS GRAVITOMETER INCLUDING A PAIR OF UPRIGHT COLUMNS OF EQUAL HEIGHT AND HAVING OPEN UPPER ENDS, EACH COLUMN HAVING A PAIR OF TELESCOPING MEMBERS SO AS TO BE VARIABLE IN HEIGHT, ONE OF THE COLUMN HAVING A GAS TO BE TESTED FLOWING THERETHROUGH, THE OTHER OF SAID COLUMNS CONTAINING AIR AT AMBIENT TEMPERATURE, PRESSURERESPONSIVE MEANS COMMUNICATING WITH THE LOWER ENDS OF THE LOWER MEMBERS OF SAID COLUMNS FOR ACTUATION BY THE DIFFERENCES IN PRESSURES AT THE BASES OF SAID COLUMNS, MEANS FOR RECORDING THE ACTUATION OF THE PRESSURE-RESPONSIVE MEANS, AND COMPENSATING MEANS RESPONSIVE TO VARIATIONS IN THE AMBIENT TEMPERATURE AND BAROMETRIC PRESSURE AND HAVING CONNECTION WITH THE UPPER MEMBERS OF SAID 